Impact type cutting device for excavating machinery



Feb. 2, 1960 w. E. MARSHALL ETAL 2,923,536

IMPACT TYPE CUTTING DEVICE FOR EXCAVATING MACHINERY Filed Aug. 25, 1958 4 Sheets-Sheet 1 ilk INVENTORS wflfacyzza/cdfialmd BY a. )"(atfie 226566 face/ope A 'T'TORN E YS W. E. MARSHALL ETAL Feb. 2, 1960 IMPACT TYPE CUTTING DEVICE FOR EXCAVATING MACHINERY Filed Aug. 25, 1958 4 Sheets-Sheet 2 INVENTORS d/mwnd 4 Katie 7Z 966cf9 wopz AT TORNEY? Feb. 2, 1960 w. E. MARSHALL ETAL 2,923,536

IMPACT TYPE CUTTING DEVICE FOR EXCAVATING MACHINERY Filed Aug. 25, 1958 4 Sheets-Sheet 5 INVENTORS 81/1046: WZa/cd/mdmd BY fic'flnu/nd a 066a Eda/ope ATTORNEYS Feb. 2, 1960 w. E. MARSHALL ET AL 2, 3, 36

IMPACT TYPE CUTTING DEVICE FOR EXCAVATING MACHINERY 4 Sheets-Sheet 4 Filed Aug. 25, 1958 wMzwWfZ wi/nd BY fid'mu/nd dfgme Q 206% f dwope AT TORNEYS IMPACT TYPE CUTTING DEVICE FOR EXCAVATING MACHINERY Walter E. Marshall and E dmund A. Kathe,

Columbus, Ohio This invention relates broadly to the art of excavating earth materials, such as coal and like minerals, and is more particularly concerned with an improved apparatus for advancing a pluralityv of cutter elements in continuous forward and reciprocally directed motions.

According to this invention, an improvement in the cost and useful life of cutting devices for excavating machinery has been found in the provision of a novel cutting head which is centrifugally carried into a stratum or seam of coal or other. ores at a relatively high rate of speed and at a high degree of impact. By employing several such heads in spaced relation, there will be a series' of rapidly occurring impacts carried out in closely adjoining paths with a resultant shattering of the coal or other mineral deposits by transitory vibrations through ,the embedded mass of coal. problem of individual operation in substantially'closed.

However, to remove the work paths, the several cutting heads are mounted in common to be reciprocally swung arcuately forwardly and rearwardly to the end that each cutter head carries out a rising and falling path of motion which, together with its motion in a circular path while it is being gradually urged forwardly, continually reduces the spaced relationship of the paths of the cutting tools. In other words, during the forward swinging motion of the cutter heads, each will repetitively cut into a thickness of coal that is reduced with each working stroke.

A principal object of the invention therefore is to provide an improved apparatus for excavating deposits of coal or like mineral ores which resides in the entry of the cutting tools into a coal vein in circular forwardly directed paths of motion and with the paths of motion being oriented to intersect the circular orbit of an ad-' jacent path.

Another object of the invention is to provide an apparatus for excavating deposits of coal wherein a plurality of cutting tools, while traversing 'a circular orbit Fatentecl F eb. 2, 1 96Q means and cutting tools rot'atably carried thereon, and

of motion at a relatively high rate of speed, are caused to engage said deposit of coal-with centrifugally induced strokes of high impact.

Another object of the invention is to provide an apparatus of the above character in which during the forward motion of the cutting tools, they traverse circular orbits of motion in paths in substantially parallel planes while being carried reciprocally upwardly and downwardly whereby the centrifugally induced cutting path, of one cutting tool will approach a-plane through the path cut by an adjacent cutting tool;

Another object of the invention is to provide a novel cutting head for excavating deposits of coal which includes a plurality of cutting tools mounted to rotate through circular paths about reversely turning shafts to impart centrifugally induced strokes of high impact and with means for swinging said cutting tools whereby a rising and falling motion will be combined to correlate the cutting strokes of adjacent cutting tools. 7 Another object of the invention is to provide a cutter head having a plurality of radially arranged supporting means for rotatingthe plurality of supporting means to centrifugally swing the cutting tools thereon intoa coal deposit with a stroke ofmajor impact.

A further object of the invention is'to provide a cutter head for mining coal or like mineral deposits having a plurality of cutting'elements adaptedto be-rotatedat high velocities to develop maximum cutting impacts by individual centrifugally induced rotation.

A still further object of the invention is to provide a cutter head of the above character wherein a plurality of cutting elements are arranged in vertically spaced relation' and rotated at high velocities to be centrifugally swung with considerable impact into the coal deposit and simultaneously reciprocally swung upwardly and downwardly whereby the thickness of a coal deposit remaining between each of the spaced cutting elements will vbe progressively reduced and continuously disintegrated by the upwardly and downwardly swinging movements.

Other objects and advantages of the invention will be-- come apparent during the course of the following tie-- 'scriptio'n when read in connection with. the accompany-- ing drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the same:

Fig. '1 is a perspective viewof cutting apparatus con-- Fig. 8 is an enlarged plan view of one of the cutting;

heads partly in section;

Fig. 9 is a side view of the cutting head;.

Fig. 10 is a perspective view of a modified form! of support arm for the cutting head; a Fig. 11 is a plan view of a cuttingdevice in which the: support arms of Fig. 10 are employed;

Fig. 12 is afront elevational view of the cutting device: of Fig. ll; and v v Fig. 13 is'a diagrammatic view of the working path: of the cutting tools. 7 I

As herein disclosed, the excavating cutter of the present invention is equipped with a plurality of radially disposed cutter heads which are caused to move in circular paths and at a high rate of speed. These cutter heads are arranged in reversely moving groups to the end that their combined cutting action is eifective to not only progressively work into' a vein of. coal or like mineral across an area of considerable width but to. collect the broken coal into a centrally disposed removal area. The work stroke of each cutter head is carried out in a highly effective impact due to'centrifugally created motion in an upward as well as a forward direction. Then during the completion of each work stroke there occurs a downward and r'earwardly directed course of motion that accomplishes rapid clearing of the work area.

Referring now to the drawings and particularly to .Figs. 1 and 2, there 'is shown a cutter device constructed inaccordance with the present invention and designated in its entirety by the numeral 20. The cutter device 20 is rigidly mounted on the forward end of a mining machine 21 and by which it is carried forwardly into the di g-3928,53 .1 b

' wardly moving caterpillar-type tractor belts. 22 and a rearwardly moving and centrally disposed conveyor 23" which is adapted to collect the brokenchunks or lumps of 1 coal at the forjward end of the :machji ne, andI convey the same rlearwardly to apointwhereitis deposited in v conventionally employed cars.

The mining or excavating cutter device 20;is essentially comprised. of a plan'ular'; vertically disposedframe .or base 24' and cutter headsgenerallydesignated by the" numerals 25 and 26.. The frame-24, is carried on the'forwardi end of thebody or -carriage?;27l;of;the mining machine 21. According to our invention,- the frame 24.is adapted to bermounted for verticalrec'iprocal movement relative to the carriage ,27 ,and 'forwthis purpose is equipped :.with trunnions 28 having spaced pairs. of ears;.2 9 ;along its upper edge, which ea'rs' ,interfit withcomplementary ears 30 formed integral with .and projecting forwardly from the carriage 27..v The'ears 29 aresuitably drilledtote- 1 function, as the machine 21 is progressively moved; for- .wardby the-tractor belts 22,;but. to also. traverse arcuate therefrom. shown in Figs. 3 and 4, one example of such positioning, which isnot intended to limit the scope of the invention, embodies arranging the several arms 40 and41 in radially spaced relation from one another according'to the number of pairs of diametrically aligned plates 52 to be mounted on the shafts.

As herein disclosed, six individual arms are arranged along the respective shafts 42 and 43 so that, in plan, as

in Fig. '3, they will be radially disposed at included angles of about 60 degrees. from one another. Also, the arms .40 and 41 are axially arranged so that the cutting ac,-

tions carried out by the cutting tools mounted in the cut? ter holders 44.will be balancedbetween the ends of each shaft42or 43. For this purpose, the six arms of each cutter head and 26 are arrangedin three diametri cally aligned pairs. Thus during one complete revolution, two cutting strokes will be made at theopposite ends ofthc 'shafts'ms well as medially therebetween. However, it is; contemplated that as many as'eight, ten

or twelvearms may be employed according to the desired working height; of the cutter. This will ofgcourse reducethe angular. relation or radial spacingfwithout.

essentially changing the vertical'spacing of the arms although this may be a matter of mechanical preference.

To maintainan equilibrium of shaft rotation, it has been found preferable to mount oneof the arms 40fand paths that sequentially overlap adjoining areas ;to be i worked. As will be more fullyhereinafter disclosed, the

cutter heads 25 and'26 accordingly completely out into and, disintegrate the'coal deposit to1be removed by upwardly and; forwardly directed strokes and operate to 41, above the uppermost bearings 47 one of each arm beneath lowermost bearings 47,

equally between the bearings 47 and sprockets 53 and54 on .theshafts .42 a ndj,.43. Each of the suitably keyed sprockets 53fan d' 54 is coupled to a related drive sprocket it 55, and- 56, by meansgof chams 57 and 58 entrainedthere;

remove thebroken coal during thedownwardly andfre'arwardly directed portions of their travel. To effect the swinging movements'of the'frame 24, it is provided on its rear surface and along the lower margin the'reofiwith router ends of piston rods 36 associated with the cylinders 33. Axles 37, supported at their ends in. the cars 34, connect the ends 35 of the piston rods to theframe 24 (Fig.- 6).;

fixedlymounted on vertically disposed shafts 42 and 43 respectively and supporting at their outer ends the .cutter bladev holders44. swill be seen in Figs.,3 and 4, the vertical shafts 42 and 43 are adapted to be rotated in contra directions inorder that the cutter holders 44 will be revolved in oppositedirectionsthrough spaced orbits of motion whereby each will enter the coal deposit while being swung forwardly and then,'while swinging rearwardly, will approach each other to guide the broken coal toward the entry end of'the conveyor 23; For this 7 purpose, the frame 24may be centrally formed to provide a passageway 45 through which thebroken coal can freely pass onto agathering pan or trough 46.. at the entryendof conveyor 23.

' spaced/pairs of ears 34 between which are receivedthe V about. Aswillbe seen' iri Fig. .6, sprockets and 56 are mounted on similar vertical shafts 59 rotatably carried in brackets 60 by means of journal sleeves61, Keyed toothe .up'per end :bf each shaft 59 is a worm gear62.

I Now, since it is intended' that the shafts 42 and 43 rotate, in contra or reverse directions, the'worm gears 62 are meshed withwornis 63 and 64 fixedly mounted on a common shaft 65. ,The worms are provided withflconveritional' spiral teethfo'rmed right? and left"' hand so that upon 'rotationjof shaft 65, said worms will drive the worm gears 62 in opposite directions. This will rotate shaft 42 counter-clockwise, as viewed in Fig. 3, while the shaft 43 will be rjotatedclockwise. While not indicated in detail, the shaftj'65 is'suitably mounted by journals in the oppositeend walls of a housing 66 andoperatively driven by a suitablesource of power, such as the motorized gear reductionunit 67. l j 1 Carried at theouter end of each arm 40 and 41 is a cutter blade holder 44' so'mo'unted that rotation ofthe related arm will effect acentrifugally created cutting action. Tothis endjeach cutter holder 44 comprises a substantially circular body 681(Figs. 8 and 9) equipped i with a radially extending lug 69 thatis rotatablymounted between the plates 52 of therespective arms 40 or 41 by fmeans of a vertical pin 70. The 'annular body 68' is The shafts 42 and .43 are rotatably mounted on the Flanges 38 and 39 by bearings 47 that are. of thesplit sleeve variety' andformed to function both as thrust bearings and rotary bearings. As shown in Fig. 7, the bearings 47 have similar half portions a and b, each of which has a flange 48 formed on the upper end thereof.

The base flanges 38 and39, as shown in Figs. 6 and 7, are provided with semi-circular cavities 49in which the bearings are received and contained thereinby retainer caps 50 mounted by bolts 51;

notched .or recessed as at 71 to receive the inner end bf a cutting tool or blade or bit 72 of a suitable tool-hardenedcutting steel. l f L 'Thelrecess or notch 71, as seen best in Fig. 8, provides a flat base surface 73 whichis disposed at a suitable angle, such asapproximately 60 degrees, to an axialline through the centerfof the body 68 and the integrally formed lug-69'thereofi The 'surface'73 terminates at one end the recess 71 whichis providedwith a short retaining flange 74having its inner surface] parallel to the basejsurface 73. e i

' Each cutting'elemeht'or'bit 72 is secured to'its related The cutter arms 40 and 41, carried by shafts. 42 and 43, comprise spaced pairs of shaped plates 52 that are rigidly secured to the shafts in axially'spaced relation between the. ends thereof andproject radially outwardly cutter head l68 by fstepping one enact said .bit into the recess 71 and seeming the same therein by means of bolts 75, withthe major length of the bit positioned against the base surface 73. The bolts 75 are. threaded at their innerlends into. a cylindrical plug 76 contained within a bore provided in the body portion Tire dlthe remaining arms :plugs 76 are preferably slightly smaller indiameter than the bore 7?. to enable easy insertion and 'to allow the same to freely move therein as the bolts are turned inwardly to secure the cutter blades. As well, the metal 'of'the plugs is selected to reduce, if not eliminate, rusting 'or freezing of the bolts therein since it is recognized that under normal Working conditions the equipment will be subjected to a considerable amount of water and/or ambient moisture.

a relieved area 79 formed in the body portion 68 of each cutter head by an inwardly directed surface 8%. By

.rnounting the cutter bits 72 in this manner, the heel end of each blade will be rigidly fitted into the cutter body 68 and held therein by bolts 75. Also during the working stroke performed by the bits, this manner of mounting will operate to resist any tendency toward loosening as the edge 78 of the cutting element is carried into the mineral vein with a high degree of impact.

The cylinders 33 (Fig. 6) are pivotally mounted by means of similar brackets 81 on the framework -27 of the mining machine 21. While not herein disclosed in detail, it is to be understood that the opposed cylinders are connected through flexible conduits indicated at 82 and 83,

to a valve controlled source of fluid power to eifect'the desired swinging movement of the frame 24 through the piston rods 36. Preferably the valve for this purpose is .an automaticallyreversible type so that continuous and alternative action of the cylinders during the mining operation is obtained. This action of the cylinders will produce forward and rearward swinging movement of the frame 24v to thereby carry or urge the cutter elements into the embedded coal deposit with a cushioning force of controllable magnitude.

As hereinabove described, the cutter device of this 'inventionincludes a pivotally mounted frame 24 that is adapted-to be carried forwardly by the tractor belts 22 0f the'rnining machine 21 and simultaneously swung forwardly and rearwardly by the cylinders 33 upon shafts --31. The cutter heads 25 and 26, carried by the frame 24,

are accordingly steadily urged forwardly into a seam or vein of coal with the cutting bits 72 thereof describing operative strokes in spaced circular paths during which the cutter bodies 68 are caused to swing upon pins 70 under a centrifugal force and thereby disintegrate the coal with considerable impact. Due to the novel mounting of the cutting tools the heretofore commonly experienced damage to the tools will be herein obviated since, while the cutter bodies, by reason of their weight, will actively force the bits 72 into the coal, in the event that a harder mineral seam is encountered, the body 68 will swing freely rearwardly on its pin 70 thereby by-passing the section of hard mineral. Also, by reason of the novel features of this invention, the circular working paths of the cutters, indicated at c in Fig. 6, which are in equally spaced planes are not the actual cutting areas through which the cutting bits 72 are carried. Thus, asindicated by the paths .d, the frame 24, in being reciprocated forwardly, actually causes the bits to move simultaneously upwardly during the cutting or disintegration of the coal. Upon comparison of the paths c and d, it becomes quite apparent that each cutter, in successive revolutions, gradually undercuts the working areas of the adjoining bits.

In considering more specific aspects of a mining machine embodying the novel features of this invention, it is believed that the practical utility thereof will become readily apparent. As graphically indicated in Figs. 6 and 13, and .by way of example only without imposing any restriction on the invention, the cutting heads 25 and 26 are adapted to carry the cutting tools 72 thereof about circular paths substantially 58 inches in diameter. As

"6 viewed in Fig. 3, the combined working areas therefore cut an area having a width of approximately :nine feet,

nine inches. Simultaneously, the amount of coal removed would result in a cut area having a height of slightly less than three feet, in the event that the cutter blades or bits 72 are caused to traverse substantially spaced circular paths; each being in a generally horizontalplane as indicated at c in Fig. 6. However, one

' of-the important advantages of the invention resides in posit.

the fact that while the blades 72 are rotated through their spaced circular paths, the frame 24is swung reciprocally forward and backward which causes the blades to ac tually follow an upwardly directed arcuate path of suffic ient length as to progressively undercut and workout the margin of coal normally untouched by cutting devices working in closed circuitous paths. This greatly reduces the amount of resistance that is encountered by each cutting blade since the adjoining blades, either disposed above or' below, will have gradually reduced the amount of coal deposit remaining therebetween. Under normally expected conditions, the swinging of the frame 24, by means of cylinders 33, through a relatively small arc or angle, as for example from 2 to 5 degrees,'will achieve this end. That is to say, each blade will traverse an upwardly directed stroke which will work-out coal in a span of 5 or 6 inches or any preferred distance between the blades in their mounted relation. I

As herein disclosed, each cutter head 25 and 2'6 .is

provided with six cutting tools 72 carried by arms 40 or 41 that are fixed to the respective shaft 42 or 43. The armsare arranged in pairs that are diametrically aligned so that there will be aradial spacing of about 60 degrees between adjacent pairs of arms. At least three cutting blades orbits 72 will be maintained in the working area .and carrying out the cutting operation while the remaining cutting blades will be in a substantially non-cutting position. By means of this arrangement, during a complete cutting cycle, or upon one full rotation of the shafts 42 and 43, an upwardly and downwardly spiralling cutting action will be effected. .This operates to maintain an equilibrium of balance during rotation of the shafts 42 and 43 which greatly reduces, if not eliminates, vibratory wearing of the bearings in which they are journaled.

Now the actual force of the cutting stroke of each cutting tool, as aforementioned, is produced by rotation of the arms 40-41 at a high rate of speed which causes the cutter holders 44 to be centrifugallyswung to carry the attached cutting bits 72 into the coaldeposit Witha considerable impact. This centrifugal force, byway of example, is induced by the mass or weight of the cutter holder 68 and the distance thereof from the axis of the respective shaft 42 or 43 By way of example, where'each 2 inches thick, it will have a weight of about 44.5 pounds. The radial length of the arms 40-'41'will be about 1 3 inches to pin 70 and 9 inches to the center of mass of the cutter holder 68; This will establish an 'over-all radius of 29 inches at the cutting edge 78 and consequently .a circularly described work path of approximately 58 inches. Thus, it may be determined that when the shafts 42-43 are rotated at approximately 200 rpm, there will be a potential force of 770 foot pounds with which each cutting blade will bedirected into themineralor coal.de-

adequate to disintegrate a vein of solid coal. During the mining operation, each blade is not responsible for a cutting action equal to its entire widthbut only that portion lodge, the .cutter holder will .be.perrnittedto .swing ljetuzv This amount of force has been found entirely line i.

'wardly about pin 70 to allow the cutting blade topass beyond the harder vein ofmateriaL- generated by a' plurality of cutting blades 72' when arranged as shown either in Figs. 3 and 4. As the mining machine 21 is propelled forwardly at a rate of about 10 inches per minute, as from vertical line e to li njef, and the frame is swung forwardly six times during the same the blades 72 will'produce rising and falling curved cutting" paths as indicated at g, h, and i. noted that the highest pointof each path approaches or l The graph shown in Fig. 13 depicts the lines of motion ment, indicated period, the highest and lowest points in the movement of It will also be passes through the lowestpoint of the path of the cutter immediately thereabove as indicated by the horizontal forward motion of the machine By varying the rate of or the rate of reciprocal motion of the cutters, the generated lines g to i inclusive will of course vary in their I generated'curves. It is likewise to be expected that-a cutting stroke will be carried out during the rising sectors of each curve and while the cutting blades are rotating forwardly and that a clearing and'coal removingf'action will occur when the cutters are rotating rearwardly in a downwardly directed course. Since the shafts 42 and 43 are rotatably driven in contra or reverse direction, the combined action of the rearwardly rotating cutting blades will effect a directing operation to carryfthe broken coal into the entry end of the conveyor 23 by which the coal is carried to cars at the rear'end of the mining machine. While the lines g to i. inclusive have beenillusti-ated as continuous rising" and falling curves, it will b'e appreciated that according to the invention disclosed-pan ticularly in Figs. 3, 4 and 6, each cuttingtool 72 carries out approximately ten forwardly andarcuately directed work strokes in the, event that, as above stated, theframe 24 is reciprocally swung' six times during ten inches forward movement of the cutters. l

In Figs. 10, 11 and 12 is disclosed a modified form of cutter device 84 which is provlded with diametrically arranged cutter holders 44 whereby two work strokes 85 and during one full rotation of the shafts 86 811(187 will be carried out by any of the vertically spacedarms I on which they are fixedly mounted; Such a structureflca'n be used to advantage in mining operations which require considerably more cutting effort to be exerted.' This is particularly true in mining or excavating harder minerals:

than coal and which characteristically have a greater resistance to'disintegration For this purpose, the arms 85 may be formed by cally opposed ends 'with suitably aligned openings; for receiving the axle pins on which the cutter holders 44 are mounted. Two cutterholders will accordingly. trav erse the samecircular cutting'path. This will materially reduce the active cutting or disintegrating effort of each cutting tool since actual width of mineral deposittobe:

removed by a cutting blade or bit during its circular and upwardly induced path of movement will" be acted-upon by two such cutting tools; one operating to' progressively produce a cutting stroke slightly above the other tool operatingin the same working path. l i

As viewed inFigs. 11 and 12, that by reason of the fact two cutter holders 44 are rotatably mounted on each arm 85, the radial or angular spacing of such modified arms will be reducedtothe end that whereas the arms 40 or 41 of Figs. 3 andjdappear in plan to be radially arranged at an, angle of approximately 60 degrees firom one another, the arms will be arranged at a lesser angle as for example of about of spaced plates 88 that are equipped at their :diametrialong its upper end, and

will become apparent drauliccylinder and a piston 8 i "drive thecutter arms thereof in circular paths while simultaneously reciprocally moving the same; l V Referring again to Fig. l3, the' curved paths of move- Ibe the same when two cutter holders 44 are mounted accordingto the modified form of cutter heads shown in Figs. 11 Y and 12, and the -efliciency of the cutter doubled by reason of'the fact heads? will practically be that there will be substantially' twowork strokescarried out in about the same path of. circular cut. Since the double cutting action will :reduce the amount of coal or other minerals engaged by .the' cutter blades on any of the arms 85, it will become apparent that less resistance to disintegration will be encountered in the'mining of hard minerals and as a ,comparably more rapid mining of coal can be eflected.

. "While the utility of the cutterdevice' of thisinvention has been particularly {described in connection with the continuous miningof such deposits as coal, analogous uses will be found in the removal of minerals having vrelatively softer physical characteristics and even seams'of a more or less rockand earth formation.

Thusthe cutter device may be employed to similar advantage in the continuous excavation of clay or dirt and rock substances in the preparation of a subterranean tunnel or, like'passageway. Likewise; excavations at surface levels can be made to :remove coal deposits according to 'such. methods known asstrip Otherwise, where desired, surface level excamining. vation work can provide substantially rectangularly formed ditches or other openings.

It is: to be understood that the forms ofithe invention herewith shownand described are to be takenas illustrative embodiments only of the same, and that various changes in the shape, size and arrangement of parts; as well as 'yarious procedural changes 'ma'y be resorted to without departing fromthe spirit-of the invention of the scope of the subjoined claims.

Weclaim: r s d 1 1. An apparatus for excavating mater-ials,-comprising a cutter head, means-for mounting said cutter head to rotate about a substantiallyvertical tool holders carried by saidcutter head for free turning movement about substantially vertical axes a cutting tool carried by each holder, means'ifor rotating said cutter head to cause thecutting' tools carried by said holders to be urged by centrifugal force intocutting engagement with the material to be removed; and means for swingingthe cutter head forwardly andLrearwardly through a' vertical arcuate path simultaneou'si withithe rotationthereof,

I 2. An apparatus forexcavating materials as claimed in claim 1, in which the first-mentioned 7 simultaneous with the rotation thereof. =9

30 degrees. Accordingly a greater amount of material I can be removed during each rotation of the cutter heads without materially increasing the power factors required to carry the cutter device 84, generally forwardly and to.

. 4. An apparatus for excavating materials as. claimed in claiml 1, in which the cutter head includesaa vertically disposedshaft and supportarms for the tool holders carried by said shaft, said support ,arrns being equally spaced along said shaft between the ends thereof "and in radially. angular relation to one another, with? each :alternate support. arm being arranged in alignment with an adjacent arm.)-

5.. .An apparatus :for excavating by lines g to'i inclusive, willgenerally axis, a plurality of about a subthe said. cutter :head

materials as claimed 9 in claim 4, in which the support arms are so located upon said shaft that the distance of forwardly and upwardly swinging movement of each of the cutting tools while in cutting engagement with the material to be removed is at least equal to the spacing between the cutting tools on said shaft.

6. An apparatus for excavating materials as claimed in claim 1, in which the cutter head includes a vertically disposed shaft and support arms for the tool holders carried by said shaft, said support arm being equally spaced along said shaft between the ends thereof and in radially angular relation to one another, the diametrically opposed ends of each support arm being equally spaced from the axis of said shaft and a tool holder being pivotally mounted on each end of each support arm for free swinging movement about a vertical axis.

7. An apparatus for excavating materials, comprising a pair of cutter heads, means for mounting said cutter heads in side-by-side relation to rotate about substantially vertical axes, each of said cutter heads including a plurality of horizontal support arms, a tool holder carried by each of said support arms for free turning movement relative thereto about a vertical axis, a cutting tool carried by each holder, means for rotating said cutter heads in opposite directions to cause the cutting tools carried by said holders to be urged by centrifugal force into cutting engagement with the material to 'be removed, and means for swinging said mounting means forwardly and rearwardly to move the cutter heads through vertical arcuate paths simultaneous with the rotation thereof.

8. An apparatus for excavating materials as claimed in claim 7, in which the last-mentioned means includes a pair of hydraulically operable cylinders and piston rods associated therewith, and means operatively connecting one end of each piston rod to the said cutter mounting means to swing the said cutter heads forwardly and rearwardly through vertical arcuate paths 'simul-' taneous with the rotation thereof in opposite-directions.

9. An apparatus for excavating materials, comprising a vertically disposed supporting frame hinged along its upper edge and having forwardly directed horizontally disposed flanges, a pair of cutter heads arranged'side by side, each including a vertically disposed shaft rotatably supported in said flanges, a plurality of horizontal support arms fixed to each shaft, a tool holder carried by each of said arms for free turning movement about a substantially vertical axis, a cutting tool carried by each holder and having a cutting edge facing in the direction of rotation of the respective cutter head, means for rotating said shafts in opposite directions to cause the cutting tools carried by said holders to be urged by centrifugal force into cutting engagement with the material to be removed, means for swinging said supporting frame forwardly and rearwardly about its upper edge to move the cutter holders and cutting tools carried thereby through a vertical arcuate path simultaneous with the rotation thereof, and means for moving the cutter heads bodily forwardly.

10. An apparatus for excavating materials as defined in claim 9, in which the support arms for the tool holders are equally spaced along each of said shafts between the ends thereof and in radially angular relation to one another.

References Cited in the file of this patent UNITED STATES PATENTS 981,201 Kuhn Jan. 11, 1911 1,195,396 Recen Aug. 22, 1916 2,653,806 Robbins Sept. 29, 1953 FOREIGN PATENTS 1,022,260 France Dec. 10, 1952 

